Density and anomalous thermal expansion of deeply cooled water confined in mesoporous silica investigated by synchrotron X-ray diffraction

Kao Hsiang Liu, Yang Zhang, Jey Jau Lee, Chia Cheng Chen, Yi Qi Yeh, Sow Hsin Chen, Chung Yuan Mou

Research output: Contribution to journalArticlepeer-review

Abstract

A synchrotron X-ray diffraction method was used to measure the average density of water (H2O) confined in mesoporous silica materials MCM-41-S-15 and MCM-41-S-24. The average density versus temperature at atmospheric pressure of deeply cooled water is obtained by monitoring the intensity change of the MCM-41-S Bragg peaks, which is directly related to the scattering length density contrast between the silica matrix and the confined water. Within MCM-41-S-15, the pore size is small enough to prevent the crystallization at least down to 130 K. Besides the well-known density maximum at 277 K, a density minimum is observed at 200 K for the confined water, below which a regular thermal expansion behavior is restored. Within MCM-41-S-24 of larger pore size, water freezes at 220.5 K. The average water/ice density measurement in MCM-41-S-24 validated the diffraction method. The anomalous thermal expansion coefficient (αp) is calculated. The temperature at which the αp reaches maximum is found to be pore size independent, but the peak height of the αp maximum is linearly dependent on the pore size. The obtained data are critical to verify available theoretical and computational models of water.

Original languageEnglish (US)
Article number064502
JournalJournal of Chemical Physics
Volume139
Issue number6
DOIs
StatePublished - Aug 14 2013

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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